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Tuesday, April 26, 2016

While responding to an RV forum question on tire performance for Class-A size tires, I found a potentially very useful web site for those in the market for new tires for Class-A RVs i.e. 22.5" sizes.

The EPA has a program called SmartWay that many may not be aware of. This program identifies tires that can provide better fuel economy than tires not on the list.

Here is the web site with the tire brand and design name of tires that are certified as meeting the minimum requirements of this regulation. Being on this list vs not being on the list is about the only tool available to tire owners to compare tires where claims have been made about improved fuel economy.

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Sunday, April 17, 2016

If you are new to the RV lifestyle or an old hand with many thousand campfires under your belt, there is one thing that is true: What you knew or learned about tires from years of car ownership probably did not prepare you for the task of maintaining the tires on your RV. This is true if your RV is a 18’ Travel Trailer or a 45’ Diesel Pusher.

I think we all understand the concept that a system is no stronger than its weakest link. For many RVs, the weakest link that can interrupt long term, problem free travel are the tires. Car tires have evolved with improved durability and reliability to the point that many people may never need to touch their tires or even know how to change a tire. Today, some cars don’t even have a spare tire and if they do the driver may not have even bothered to learn where it is as the expectation of needing to use the spare is so low it has completely dropped off the radar screen.

As a retired Tire Engineer with 40 years experience in design, evaluation and quality assurance of tires I would like to offer some suggestions that I believe if followed, will lead to many years of problem free travel. I also believe that once you take the initial steps I outline, you will also find that you will only need to spend about 15 minutes a month, or less on average with tire maintenance.

The basics that are needed to have a tire problem free experience with your RV tires involve two simple steps:

1. Knowing the proper level of tire inflation on your personal RV and

2. Ensuring your tires are always inflated to that level.

There it is, just two simple and rather basic steps and, you don’t need to be experienced in vehicle mechanics or tire engineering to accomplish these two steps as I am going to share the steps that have worked for me and thousands of others for decades.

Step 1: Knowing Your Proper Inflation

So the first step is to know the proper level of tire inflation on your personal RV. The important concept here is “Your RV”. Not the RV your brother-in law uses, or the inflation the guy in the campsite next to you uses, or even the level provided by the RV manufacturer on the tire certification label, otherwise know as the “Tire Placard”. Now some will point out that the RV manufacturer has the responsibility to inform you of the minimum tire inflation you should use, and this is correct, but this is based on an assumption which may mean the numbers are too high or too low for your RV when you have it packed with the stuff you want to take along on your next trip.

This step takes the most effort, but you really only need to do it once over the years you own your RV – unless you make a major change such as add a generator or refinish the interior with granite counter tops; you know, do something that significantly changes the weight of the RV.

To learn your real weight you need to pack your RV with all the clothes, food, fuel, water and other “stuff” you expect to carry, including the proverbial "bowling ball collection." Once it is fully loaded, you and the family need to take a short trip to a local feed store or gravel pit or truck stop that has a large truck scale with enough side clearance that will allow you to get the tires from just one side of the RV on the scale. Obviously you will need to do a bit of preparation to find such a scale, so some time on the Internet or with a phone book is in order. It is suggested that you review the worksheet before heading off to the scale so you get all the facts you need in one trip.

Here is a company that travels the US and specializes in properly weighing RVs and giving the owner the load numbers for their personal unit." RV Safety & Education Foundation (RVSEF) This leader in safety education in the RV community offers wheel by wheel RV weighing services for all types of RVs.

Resources

If you will not be in one of the locations where RVSEF is offering their services then you will need to do a little research, as not all truck scales have the side clearance needed. You should know that some truck scale operators discourage side to side weights and have installed guard rail to prevent this. When you check out the work sheet you will have a better understanding of what is needed.

Our friends at Fifthwheel St have a web site has information including a video that focuses on trailers but has video showing the process which is similar for motorhomes.

Bridgestone has a page just on RV tires with a worksheet for calculating tire loads

If you look at more than one of the above links I think you will see that everyone offers the same basic information on the process. You do not need to worry about which worksheet you use as the math is the same for everyone.

After you complete your worksheet you should know the actual load on each tire position. The next step is much easier and also only needs to be done once. You need to confirm the minimum cold inflation your tires need to carry the load. It is always a good idea to use the tables published by your brand tire. Here is my blog page with links to many different brand tires. Simply go to your brand, find the table that has your size tire and look for the inflation that supports your load or more. Don't worry if your brand doesn't offer tables as almost all companies follow the same published industry standards.

Also don’t be tempted to go to a lower level of inflation if your numbers are close. Always go up.

Now you know the minimum Cold Inflation Pressure or CIP.Wait! What do I mean by CIP? Whenever tire inflation pressure is measured or set the tire needs to be cool and at the same temperature of the air and in the shade. This means not having been driven on or in direct sunlight for at least 2 to 3 hours. Tires get warm when moving and the Sun heats them up which results in a higher temperature which results in artificial increase in pressure. Many people simply do their tire pressure check in the morning before starting out or late evening after a day of travel. Either way the tire needs to be cool and in the shade when you check your pressure.

I feel the CIP needs to above the minimum needed to carry the load as if there is a drop in temperature you may end up below the minimum if you cut things too close. I suggest you run +10% above the Minimum for your personal CIP.

A couple of details and a suggestion:

All tires on each axle should have the same inflation. This means that whatever inflation numbers you have for your tires select the highest from the tires on any one axle and use that number for all tires on that axle. This will give you more uniform stopping and steering response.

Over the past few years technology has evolved that allows you to monitor your tire inflation as you drive down the road and can warn you if you pick up a nail or other damage. You have this in your car and it is that little orange symbol with the exclamation point in it.

and now you can add this safety feature to your RV trailer or motorhome. It is called a Tire Pressure Monitor System or TPMS for short. A quick internet search will identify a number of units specifically designed for RV application or you can review THIS web site for a discussion of features to consider when shopping for a TPMS.A bit of Truth in Advertising here. This blog is currently sponsored by Tire Traker brand TPMS. As you might expect that is the brand I have run for years. What you may not know is that I bought my TPMS from Traker before I started writing this blog.
One nice feature of having such a system is you do not need to get out with your digital pressure gauge and check your tires every day of travel as the TPMS will let you know your inflation in the morning while you stay inside with your coffee and more importantly while going down the road. You will quickly learn the details of your pressure reading in just a few days of observation.

So there you have it. Get the RV weighed when fully loaded and do the calculations using the worksheet to learn the actual tire loading and the inflation your tires need.

Step 2: Ensuring That Inflation Is Properly Maintained

This step is much more straightforward. Just check your tire pressure every travel day, or better yet get and use a TPMS (Tire Pressure Monitoring System)to constantly monitor your tire pressure. I even set my low pressure alarm level so I would get a warning before the pressure drops below the minimum inflation I need to support the measured load on my RV.

I believe that if you follow this advice you should reduce what otherwise might be a less than 5% chance of having a tire failure to less than ½% chance of tire failure.

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Tuesday, April 12, 2016

Just got an email from a reader, in which he describes a recent tire failure he experienced on his travel trailer. He reported:

"Mr Marble,I recently experienced a catastrophic tire blowout. I am 100% confident it was not due to low tire pressure (according to my tpms). My tpms did not alert me to an overheat or pressure issue. I was only 35 miles into my trip. It alerted to the blowout 3-5 seconds after the blowout, but I had already heard the pop and saw tire and fender shrapnel flying in my side view mirror. It was passenger front tire on trailer.Tires are approx three ears old, around 5000 miles on them. We are weekend warriors plus 1-2 1000 mile trips per year. Rig sits 2-4 months of the year under shed cover with covers on tires on gravel.Before I go in to details on rig and such, would you be willing to give me your opinion as to the cause of the failure? I have my suspicions but I'd like to hear from an expert.I put the spare on and finished my trip and am sitting at ocean lakes family campground in Myrtle beach. Can take pics/video and provide whatever data you need.Here's a couple of pics if it helps sway your decision.RW-Myrtle Beach"

Here are the pictures he sent of his tire.

Now many of you might think these are sufficient but for me to provide a better more accurate opinion of that went wrong I really do need better pictures.

In this case it was too late to get better pictures as RW informed me that he didn't have room to save the tire till he got home.

A few comments and observations.

The tire did not suffer a "Run Low Flex Failure" or what is normally called a "Blowout" by a non-tire engineer. The condition of the tire is more accurately a Tread or Belt Separation. The air loss came after the belts and tread had already separated from the body or carcass of the tire so that is why the TPMS did not provide any warning.

I did inform RW that the pictures were not close enough or of high enough quality to allow me to zoom in to see the details needed for me to establish a reason for the failure with a high degree of confidence but I did provide some comments.

A tire suffering a Tread Separation is simply not going to generate high enough temperature to trigger the TPMS.

It appears that this tire possibly suffered from some manufacturing or chemical problem as there are large amounts of steel cord with no rubber adhering to the steel cords. This could be because the tire had started to separate many miles prior to the external failure and the rubber was abraded from the steel cord. I would need to do microscopic examination to confirm this diagnosis.

I also suggested that he include the Free Spin inspection procedure at least once a year so he would improve his chance of discovering an impending tire failure in the future.

A side comment about retaining the tire. If RW had wanted to file a warranty claim with the RV dealer or tire company he would need to be able to produce the tire for examination. It would also have been a good idea to be sure he had recorded the complete DOT serial and file a complaint with NHTSA for without complaints there will never be an investigation or a possibility of a recall or an improvement in the quality of tires produced for the RV market.

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Recently saw a post on another blog Tires and Burst Pressure, What causes a "blowout". Now there was nothing really w...

About RogerBefore retiring, Roger Marble spent 40 years in the tire industry, working for a major manufacturer developing tires for applications in North, Central and South America. During his career he worked on many kinds of tires -- heavy truck, passenger, light truck and Indy-car types. If you have a question for Roger, email him at tireman9(at)gmail.com. or click on this icon to subscribe and get a notice as soon as there is a new post. (about once a week).
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